1. Field of the Invention
This invention relates to a tape cassette and, more particularly, to a tape cassette including a casing or cassette consisting of upper and lower half casing portions integrally connected to each other, and a plug for preventing erasure by mistake which separate from said casing. The plug is insertable in one or another preselected direction into an engagement recess provided in said casing so that the tape cassette may be used for recording or to make erasure impossible depending on the selected direction in which the plug is introduced into the engagement recess.
2. Description of the Prior Art
In many currently used compact type tape cassettes, an opening for preventing erasure by mistake is provided on the back side of a cassette consisting of interconnected upper and lower half portions. A mistake erasure inhibiting tab is implanted on the upper half portion or lower half portion so as to cover said inhibiting opening. A mistake erasure inhibiting pawl is provided in the tape recorder so as to enter said mistake erasure inhibiting opening when the tape cassette is mounted in position in the tape recorder. If desired to prevent the tape cassette from being erased, that is, to protect the magnetic tape against mistaken erasures, the tab is broken off manually to open the mistake erasure inhibiting opening so as to permit the mistake erasure inhibiting pawl to enter said opening to prevent erasures by mistake of the tape cassette.
With such conventional tape cassettes, if it is desired to place the tape cassette in the recording condition after the pawl has already broken off, a piece of tape may be bonded to the opening or the opening may be filled with a suitable pad so that the pawl of the tape recorder may not enter the erasure inhibiting opening.
In such prior art devices, it is not possible to completely fill the mistake erasure inhibiting opening, which can cause erroneous operations. Moreover, the bonded tape pieces or pads may occasionally enter the inside of the tape recorder thus causing malfunctions of the device. In addition, for certain types of the materials of the cassette, breaking off of the projection may involve considerable labor and cause operational difficulties.
In tape cassettes used as recording mediums for e.g. an electronic computer, it is also known to use a U-shaped mistake erasure inhibiting plug that may be introduced into a mistake erasure inhibiting opening provided in the cassette. By selecting the direction in which the plug is introduced into the erasure inhibiting opening it may be opened or closed so as to make tape cassette recording possible or impossible.
Such erasure inhibiting devices involve certain inconveniences in that the erasure inhibiting opening is provided in the normally invisible back side of the cassette so that the user may not realize instantly whether or not the tape cassette is recording correctly. Especially, when the tape cassette is mounted to the tape recorder, the back side of the tape cassette is completely buried in the tape recorder and hidden from the user's view. Hence, whenever the tape cassette is used, it may be necessary to remove the tape cassette from the tape recorder in order to check whether the tape cassette can be used for recording or not, thus resulting in inconvenience during operation.